The instrument panel of an automotive vehicle is supported above the floor pan of the vehicle by a centrally positioned support brace that extends upwardly from the floor pan hump to connect with the central part of the instrument panel. Low frequency vibrations, e.g. vibrations in the range of 25-75 Hz, can be transmitted from the floor pan, through the central support brace and into the instrument panel, where this low frequency vibration can be felt by the operator through the steering wheel. Although this vibration is detected via gripping the steering wheel, this low range vibration is chassis generated and transmitted from the floor pan through the instrument panel supports to the cross car beam and, ultimately, to the steering wheel. This low range vibration should be suppressed.
The steering column is isolated from the instrument panel by rubber seals and rubber grommets in U.S. Pat. No. 2,549,925, issued to Clyde Paton on Apr. 24, 1951, and in U.S. Pat. No. 3,300,229, issued to Floyd Kishline on Jan. 24, 1967, to restrict the transmission of vibrations from the instrument panel and related structure to the steering column, and ultimately transmission to the steering wheel to be detected by the operator. In U.S. Pat. No. 2,741,324, granted to Ralph Anderson on Apr. 10, 1956, the instrument panel is supported by a rubber grommet that connects to the windshield frame to prevent the transmission of vibrations and shocks to the instrument panel. Interrupting the transmission of vibrations through the vehicle body through rubber isolating body mounts is well known in the automotive art, such as is reflected in U.S. Pat. No. 3,181,850, issued on May 4, 1965, to Jacques Bajer.
Energy absorbing members formed of elongated steel straps which sandwich a viscoelastic pad between them have been used in controlling body shake in automobiles, as is disclosed in U.S. Pat. No. 3,211,491, granted on Oct. 12, 1965, to Horace Browne, et al. In the Browne structure, the two steel straps can be fastened together with rivets or bolts so that the elastomeric pad between the two steel straps can absorb shake energy at the front end of the vehicle. In U.S. Pat. No. 5,951,087, issued to D. Scott Bittinger on Sep. 14, 1999, a rubber boot is configured to secure the underside of the instrument panel and to receive the cross car beam to limit the transmission of vibrations between the cross car beam and the instrument panel. The steering column can also be vibrationally isolated by mounting structure that can contain an elastomeric filler material to improve the dampening characteristics of the steering column, as is taught in U.S. Pat. No. 6,692,026, granted on Feb. 17, 2004, to Nicholas Gianaris, et al.
Rubber isolators are used at the bottom of the center support brace structure of an automotive vehicle to prevent vibrations transfers to the support brace, as is shown in U.S. Patent Application Publication No. 2006/0017310 of Jae Kap Joo, et al, published on Jan. 26, 2006. Such dampening structure is not practical in automotive assembly as the installation of the rubber bushings would be very difficult to accomplish. Furthermore, the placement of the elastomeric isolators near the floor pan raises concerns as to the deterioration of the elastomeric members due to heat from the exhaust system that is transmitted through the floor pan. Elastomeric bushings isolate the steering column in U.S. Patent Application Publication No. 2006/0278030, published on Dec. 14, 2006.
It would be desirable to provide a support brace structure that can be utilized in a configuration in which low frequency vibrations are to be prevented from being transmitted to the automotive component being supported by the support braces. It would be desirable if this support brace structure would position the vibration dampening material away from the floor pan without requiring a revision in the current assembly process.